Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$128.69	10.505%	$142.2089	$142.21	$142.20	$142.20
Purchase #2	$231.99	12.234%	$260.3717	$260.37	$260.35	$260.40
Purchase #3	$147.78	9.523%	$161.8531	$161.85	$161.85	$161.90
Purchase #4	$146.78	12.779%	$165.537	$165.54	$165.55	$165.50
Purchase #5	$67.61	13.680%	$76.859	$76.86	$76.85	$76.90
Purchase #6	$130.53	8.771%	$141.9788	$141.98	$142.00	$142.00
Purchase #7	$88.83	12.825%	$100.2224	$100.22	$100.20	$100.20
7 purchase totals =	$942.21		$1,049.0309	$1,049.03	$1,049.00	$1,049.10